A battery

Abstract

The present invention relates to the field of new energy batteries, and specifically to a battery, the battery comprising an electrode sheet; wherein the electrode sheet comprises a current collector, a functional layer and an active material layer, the functional layer is arranged on at least one surface of the current collector along the thickness direction, and the active material layer is arranged on the surface of the functional layer away from the current collector; the functional layer comprises a conductive agent and a thermally polymerizable monomer; the electrode sheet is a positive electrode sheet and / or a negative electrode sheet. The battery of the present invention can ensure the electron transmission of the battery cell at normal temperature, and can also make the thermally polymerizable monomer polymerize at high temperature through thermal response before thermal runaway, thereby causing volume expansion, thereby causing the conductive agent to disconnect, isolating the electron interaction, and thus improving the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the field of new energy batteries, and in particular to a battery having a composite positive electrode sheet and / or a composite negative electrode sheet. Background Art

[0002] As the energy density of the battery cell increases, the risk of thermal runaway of the battery cell also gradually increases. Generally speaking, the risk of thermal runaway of the battery cell comes from the side reactions caused by the ion interaction inside the battery cell, which leads to the decomposition of a large amount of exothermic diaphragm, thus causing internal short circuit.

[0003] Based on the above problems, technicians in this field have proposed to construct electrolyte solidification technology under high temperature inside the battery cell to isolate internal ion interactions and thus improve the safety performance of the battery. However, there is currently no research on isolating electron interactions from the electrode level to avoid internal short circuits inside the battery cell to improve the safety performance of the battery. Summary of the invention

[0004] In view of this, the present invention is dedicated to providing a battery to solve the problem in the prior art that ion interactions inside the battery cell easily induce side reactions, resulting in reduced battery safety performance.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] The present invention provides a battery, the battery comprising an electrode sheet;

[0007] The electrode sheet comprises a current collector, a functional layer and an active material layer, wherein the functional layer is arranged on at least one surface of the current collector along the thickness direction, and the active material layer is arranged on the surface of the functional layer away from the current collector; the functional layer comprises a conductive agent and a thermally polymerizable monomer;

[0008] The electrode sheet is a positive electrode sheet and / or a negative electrode sheet.

[0009] Optionally, the thickness of the functional layer is 2-8 μm; preferably, the thickness of the functional layer is 3-6 μm.

[0010] Optionally, in the functional layer, the conductive agent and the thermal polymerization monomer satisfy the relationship: 10≤W1 / W2≤20, wherein W1 represents the mass proportion of the thermal polymerization monomer in the functional layer, and W2 represents the mass proportion of the conductive agent in the functional layer; preferably, the conductive agent and the thermal polymerization monomer satisfy the relationship: 13≤W1 / W2≤17.

[0011] Optionally, the thermally polymerizable monomer contains an unsaturated bond; optionally, the unsaturated bond includes at least one of a carbon-carbon double bond, a carbon-carbon triple bond and a cyclic monomer.

[0012] Optionally, the thermally polymerizable monomer is selected from at least one of acrylamide, N,N-dimethylbisacrylamide, bismaleimide and nadic anhydride.

[0013] Optionally, the conductive agent includes a one-dimensional conductive agent; optionally, the radial length of the one-dimensional conductive agent is 0.5-8 μm, preferably 2-4 μm.

[0014] Optionally, the one-dimensional conductive agent is selected from at least one of carbon fiber, carbon nanotube and copper nanotube.

[0015] Optionally, the battery further comprises a non-aqueous organic electrolyte, wherein the non-aqueous organic electrolyte contains an initiator.

[0016] Optionally, the initiator and the thermal polymerization monomer satisfy the following relationship: W3 / W4≤0.05, wherein W3 represents the mass of the initiator in the non-aqueous organic electrolyte, and W4 represents the mass of the thermal polymerization monomer in the battery; preferably, the initiator and the thermal polymerization monomer satisfy the following relationship: 0.01≤W3 / W4≤0.03.

[0017] Optionally, the initiator is selected from dibenzoyl peroxide and / or azobisisobutyronitrile.

[0018] Through the above technical scheme, the beneficial technical effects of the present invention are as follows: the battery of the present invention includes an electrode sheet, which includes a current collector, a functional layer and an active material layer, wherein the functional layer is arranged between the current collector and the active material layer; the functional layer includes a conductive agent and a thermal polymerization monomer. By arranging the functional layer in the electrode sheet, it is possible to ensure that electrons are transmitted at normal temperatures of the battery cell without affecting the electrical performance, and it is also possible to achieve thermal response before thermal runaway, so that the thermal polymerization monomers are polymerized at high temperatures and then induce rapid volume expansion, thereby causing the conductive fibers to be disconnected, isolating the electronic interaction of the battery cell, thereby improving safety performance and reducing the risk of thermal runaway.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The present invention discloses a battery, and those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0021] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A, B are listed, the phrase "at least one of A, B" means only A; only B; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0022] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0023] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0024] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0025] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or included, or may only include or include the listed components.

[0026] In order to solve the risk problem of battery thermal runaway in the prior art, the present invention adopts the following technical solution:

[0027] The present invention provides a battery, the battery comprising an electrode sheet;

[0028] The electrode sheet comprises a current collector, a functional layer and an active material layer, wherein the functional layer is arranged on at least one surface of the current collector along the thickness direction, and the active material layer is arranged on the surface of the functional layer away from the current collector; the functional layer comprises a conductive agent and a thermally polymerizable monomer;

[0029] The electrode sheet is a positive electrode sheet and / or a negative electrode sheet.

[0030] The battery in the present invention comprises a battery cell, wherein the battery cell is provided with a functional layer between the current collector and the active material layer, the functional layer comprising a conductive agent and a thermally polymerizable monomer. The functional layer can ensure electron transmission of the battery cell at normal temperature, and can also polymerize the thermally polymerizable monomer at high temperature through thermal response before thermal runaway, thereby inducing volume expansion, thereby causing the conductive agent to disconnect, isolating electron interaction, and thereby improving the safety performance of the battery.

[0031] According to the present invention, the thickness of the functional layer can be 2~8μm. Exemplarily, the thickness of the functional layer can be any value among 2μm, 3μm, 4μm, 5μm, 6μm, 7μm and 8μm, or any value within the range of values ​​composed of any two of the above values. In the present invention, if the thickness of the functional layer is too large, the weight of the pole piece will increase, the energy density of the system will be reduced, and the impedance will also be increased, thereby increasing the polarization of the battery cell, which is not conducive to the performance of electrical performance; if the thickness of the functional layer is too small, the volume expansion will be small after thermal polymerization, and thus a good electronic isolation effect will not be achieved. Preferably, the thickness of the functional layer is 3~6μm.

[0032] According to the present invention, the appropriate ratio of conductive agent and thermal polymerization monomer can, on the one hand, ensure the electronic transmission of the battery cell without affecting the electrical performance; on the other hand, it can be thermally responded before thermal runaway, so that the thermal polymerization monomer is polymerized at high temperature and then causes rapid volume expansion, thereby causing the conductive agent to disconnect and isolate the electronic interaction of the battery cell, thereby improving safety performance and reducing the risk of thermal runaway. In the functional layer, the conductive agent and the thermal polymerization monomer can satisfy the relationship: 10≤W1 / W2≤20, wherein W1 represents the mass proportion of the thermal polymerization monomer in the functional layer, and W2 represents the mass proportion of the conductive agent in the functional layer. In the present invention, if the W1 / W2 ratio is too high, that is, the amount of conductive agent added is insufficient, it will affect the electronic transmission; if the W1 / W2 ratio is too low, that is, the amount of thermal polymerization monomer added is insufficient, it will affect the improvement effect of thermal runaway. Preferably, the conductive agent and the thermal polymerization monomer satisfy the relationship: 13≤W1 / W2≤17.

[0033] According to the present invention, the thermally polymerizable monomer contains an unsaturated bond, and the unsaturated bond in the thermally polymerizable monomer enables the thermally polymerizable monomer to polymerize at a high temperature. Exemplarily, the unsaturated bond may include at least one of a carbon-carbon double bond, a carbon-carbon triple bond, and a cyclic monomer.

[0034] Exemplarily, the thermally polymerizable monomer may be selected from at least one of acrylamide, N,N-dimethylbisacrylamide, bismaleimide and nadic anhydride.

[0035] According to the present invention, the conductive agent preferably includes a one-dimensional conductive agent. The one-dimensional conductive agent selected in the present invention can greatly improve the electron transport effect.

[0036] In the present invention, the radial length of the one-dimensional conductive agent can be 0.5~8μm. Exemplarily, the radial length of the one-dimensional conductive agent can be any value among 0.5μm, 2μm, 4μm, 6μm and 8μm, or any value within the range of values ​​composed of any two of the above values. In the present invention, if the radial length of the one-dimensional conductive agent is too large, after the volume expansion of the functional layer due to thermal polymerization, there is a greater probability that the conductive agent will be connected, and the effect of electronic insulation cannot be achieved. If the radial length of the one-dimensional conductive agent is too small, it is easy to agglomerate in the functional layer and is not easy to disperse, resulting in increased polarization of the functional layer, which is not conducive to the performance of electrical properties. Preferably, the radial length of the one-dimensional conductive agent is 2~4μm.

[0037] Exemplarily, the one-dimensional conductive agent may be selected from at least one of carbon fiber, carbon nanotube and copper nanotube. In order not to affect electron transport, the present invention preferably uses a one-dimensional conductive agent with a large specific surface area.

[0038] According to the present invention, the battery may further include a non-aqueous organic electrolyte, wherein the non-aqueous organic electrolyte contains an initiator. The present invention uses a non-aqueous organic electrolyte containing an initiator, and after injection, the non-aqueous organic electrolyte can infiltrate the electrode functional layer, and the initiator, as a reaction medium, can improve the reaction efficiency of the thermal polymerization monomer at high temperature.

[0039] In the present invention, if the initiator content in the non-aqueous organic electrolyte is too high, side reactions are likely to occur in the electrolyte, resulting in increased impedance and affecting the electrical performance of the battery; if the initiator content in the aqueous organic electrolyte is too low, it will affect the polymerization effect of the thermal polymerization monomer, resulting in a decrease in the thermal runaway temperature. Exemplarily, the initiator and the thermal polymerization monomer may satisfy the following relationship: W3 / W4≤0.05, wherein W3 represents the mass of the initiator in the non-aqueous organic electrolyte, and W4 represents the mass of the thermal polymerization monomer in the battery; preferably, the initiator and the thermal polymerization monomer satisfy the following relationship: 0.01≤W3 / W4≤0.03.

[0040] According to the present invention, the initiator may be selected from dibenzoyl peroxide and / or azobisisobutyronitrile.

[0041] As a first embodiment of the present invention, the electrode sheet with a functional layer is a positive electrode sheet. Exemplarily, the positive electrode sheet includes a positive current collector, a positive functional layer and a positive active material layer, the positive functional layer is arranged on at least one surface of the positive current collector along the thickness direction, and the positive active material layer is arranged on the surface of the positive functional layer away from the positive current collector. In this embodiment, the positive electrode functional layer includes a first conductive agent and a first thermopolymer monomer, wherein the first thermopolymer monomer contains a first unsaturated bond, and the first conductive agent includes a first one-dimensional conductive agent; in the positive electrode functional layer, the first conductive agent and the first thermopolymer monomer satisfy the relationship: 10≤W 1正极 / W 2正极 ≤20,W 1正极 represents the mass proportion of the first thermally polymerized monomer in the positive electrode functional layer, W 2正极 Represents the mass proportion of the first conductive agent in the positive electrode functional layer. The positive electrode active material contained in the positive electrode active material layer of the present invention may be well known to those skilled in the art, for example, may include but is not limited to ternary lithium battery positive electrode material, lithium iron phosphate positive electrode material, lithium iron manganese phosphate positive electrode material and ternary sodium battery positive electrode material. The thickness of the positive electrode active material layer of the present invention may be well known to those skilled in the art, and illustratively, the single-sided thickness of the positive electrode active material layer may be 15 to 70 μm.

[0042] As a second embodiment of the present invention, the electrode sheet with a functional layer is a negative electrode sheet. Exemplarily, the negative electrode sheet includes a negative electrode current collector, a negative electrode functional layer and a negative electrode active material layer, the negative electrode functional layer is arranged on at least one surface of the negative electrode current collector along the thickness direction, and the negative electrode active material layer is arranged on the surface of the negative electrode functional layer away from the negative electrode current collector. In this embodiment, the negative electrode functional layer includes a second conductive agent and a second thermopolymerizable monomer, the second thermopolymerizable monomer contains a second unsaturated bond, and the second conductive agent includes a second one-dimensional conductive agent; in the negative electrode functional layer, the second conductive agent and the second thermopolymerizable monomer satisfy the relationship: 10≤W 1负极 / W 2负极 ≤20,W 1负极 represents the mass proportion of the second thermally polymerizable monomer in the negative electrode functional layer, W 2负极 Indicates the mass proportion of the second conductive agent in the negative electrode functional layer. The negative electrode active material contained in the negative electrode active material layer of the present invention may be well known to those skilled in the art, for example, may include but is not limited to graphite, silicon-based materials and hard carbon materials. The thickness of the negative electrode active material layer of the present invention may be well known to those skilled in the art, and illustratively, the single-sided thickness of the negative electrode active material layer may be 20 to 80 μm.

[0043] As a preferred embodiment of the present invention, both the positive electrode sheet and the negative electrode sheet in the battery of the present invention have a functional layer. In this preferred embodiment, the electronic interaction before thermal runaway can be isolated to the greatest extent to improve the safety performance of the battery. Exemplarily, the positive electrode sheet includes a positive current collector, a positive electrode functional layer and a positive electrode active material layer, the positive electrode functional layer is arranged on at least one surface of the positive current collector along the thickness direction, and the positive electrode active material layer is arranged on the surface of the positive electrode functional layer away from the positive current collector. The negative electrode sheet includes a negative current collector, a negative electrode functional layer and a negative electrode active material layer, the negative electrode functional layer is arranged on at least one surface of the negative current collector along the thickness direction, and the negative electrode active material layer is arranged on the surface of the negative electrode functional layer away from the negative current collector. Specifically, the positive electrode functional layer includes a first conductive agent and a first thermal polymerizable monomer, wherein the first thermal polymerizable monomer contains a first unsaturated bond, and the first conductive agent includes a first one-dimensional conductive agent; in the positive electrode functional layer, the first conductive agent and the first thermal polymerizable monomer satisfy the relationship: 10≤W 1正极 / W 2正极 ≤20,W 1正极 represents the mass proportion of the first thermally polymerized monomer in the positive electrode functional layer, W 2正极 The negative electrode functional layer includes a second conductive agent and a second thermopolymerizable monomer, wherein the second thermopolymerizable monomer contains a second unsaturated bond, and the second conductive agent includes a second one-dimensional conductive agent; in the negative electrode functional layer, the second conductive agent and the second thermopolymerizable monomer satisfy the relationship: 10≤W 1负极 / W 2负极 ≤20,W 1负极 represents the mass proportion of the second thermally polymerizable monomer in the negative electrode functional layer, W 2负极 Indicates the mass proportion of the second conductive agent in the negative electrode functional layer. Further preferably, the battery further comprises a non-aqueous organic electrolyte, the non-aqueous organic electrolyte contains an initiator, and the initiator and the thermal polymerization monomer can satisfy the following relationship: W3 / W4≤0.05, wherein W3 represents the mass of the initiator in the non-aqueous organic electrolyte, and W4 represents the total mass of the first thermal polymerization monomer and the second thermal polymerization monomer contained in the battery.

[0044] The present invention also provides a method for preparing a double-layer coated positive electrode sheet, which may include the following steps:

[0045] S11, after mixing the positive electrode active material, the positive electrode binder and the positive electrode conductive agent, adding the positive electrode solvent and stirring to obtain a positive electrode slurry; mixing the first conductive agent and the first thermal polymerization monomer to obtain a positive electrode functional layer slurry;

[0046] S12, coating the positive electrode functional layer slurry on at least one surface of the positive electrode current collector along the thickness direction to obtain a positive electrode current collector coated with the positive electrode functional layer slurry; performing a first drying treatment on the positive electrode current collector coated with the positive electrode functional layer slurry to obtain a positive electrode current collector having a positive electrode functional layer on the surface;

[0047] S13, coating the positive electrode slurry on the surface of the positive electrode functional layer away from the positive electrode current collector to obtain a double-layer coated positive electrode current collector, and drying, rolling and slitting the double-layer coated positive electrode current collector.

[0048] The present invention has no particular restrictions on the type of positive electrode conductive agent, which can also be selected by conventional technology. As an example, the positive electrode conductive agent includes but is not limited to superconducting carbon, conductive graphite, conductive carbon black (including acetylene black, Ketjen black, etc.), carbon nanotubes (including single-walled carbon nanotubes and / or multi-walled carbon nanotubes), graphene or carbon fiber. One or more combinations. The present invention has no particular restrictions on the type of positive electrode binder, which can also be selected by conventional technology. As an example, the positive electrode binder includes but is not limited to one or more combinations of sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, etc. The positive electrode solvent in the present invention can be N-methylpyrrolidone. The present invention does not limit the specific materials, structures, etc. of the positive electrode current collector and the positive electrode active material in the positive electrode sheet. The positive electrode sheet structure and composition that are known in the art and can be used for batteries can be selected, which will not be repeated here.

[0049] The present invention also provides a method for preparing a double-layer coated negative electrode sheet, which may include the following steps:

[0050] S21, after mixing the negative electrode active material, the negative electrode thickener, the negative electrode binder and the negative electrode conductive agent, adding the negative electrode solvent and stirring to obtain a negative electrode slurry; mixing the second conductive agent and the second thermal polymerization monomer to obtain a negative electrode functional layer slurry;

[0051] S22, coating the negative electrode functional layer slurry on at least one surface of the negative electrode current collector along the thickness direction to obtain a negative electrode current collector coated with the negative electrode functional layer slurry; subjecting the negative electrode current collector coated with the negative electrode functional layer slurry to a second drying treatment to obtain a negative electrode current collector having a negative electrode functional layer on the surface;

[0052] S23, coating the negative electrode slurry on the surface of the positive electrode functional layer away from the negative electrode current collector to obtain a double-layer coated negative electrode current collector, and drying, rolling and slitting the double-layer coated negative electrode current collector.

[0053] The present invention has no particular restrictions on the type of negative electrode conductive agent, which can also be selected by conventional technology. As an example, the negative electrode conductive agent includes but is not limited to superconducting carbon, conductive graphite, conductive carbon black (including acetylene black, Ketjen black, etc.), carbon nanotubes (including single-walled carbon nanotubes and / or multi-walled carbon nanotubes), graphene or carbon fiber. One or more combinations. The present invention has no particular restrictions on the type of negative electrode binder, which can also be selected by conventional technology. As an example, the negative electrode binder includes but is not limited to one or more combinations of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, etc. The negative electrode thickener in the present invention can be sodium carboxymethyl cellulose, and the negative electrode solvent in the present invention can be deionized water. The present invention does not limit the specific materials, structures, etc. of the negative electrode current collector and the negative electrode active material in the negative electrode plate. The negative electrode plate structure and composition that are known in the art and can be used for batteries can be selected, which will not be repeated here.

[0054] In one embodiment of the present invention, the preparation method of the electrolyte in the present invention may include: preparing a non-aqueous organic electrolyte in a glove box filled with an inert gas, and adding an initiator to the non-aqueous organic electrolyte. The non-aqueous organic electrolyte in this embodiment can be selected from the components of the non-aqueous organic electrolyte that can be used for batteries that are well known in the art, and will not be described in detail here.

[0055] In the present invention, the battery structure includes but is not limited to button batteries, soft-pack batteries, cylindrical batteries, etc.

[0056] In one embodiment of the present invention, the battery in the present invention may be a soft-pack battery, and the preparation method of the soft-pack battery may include: stacking a double-layer coated positive electrode sheet, a separator, and a double-layer coated negative electrode sheet in order, ensuring that the separator is between the double-layer coated positive electrode sheet and the double-layer coated negative electrode sheet to play an isolating role, placing the bare battery cell in an outer package to obtain a battery cell. Injecting a non-aqueous organic electrolyte into the dried battery, encapsulating, standing and forming, and then performing secondary encapsulation, standing and volume separation.

[0057] The present invention is further described in detail by way of examples. The raw materials used in the examples can be obtained through commercial sources.

[0058] Example 1

[0059] (1) Preparation of double-layer positive electrode sheet: N,N-dimethylbisacrylamide and carbon nanotubes are mixed into NMP solvent at a mass ratio of 15:1, and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode functional layer slurry with uniform fluidity. After the positive electrode active material ternary layered positive electrode, binder polyvinylidene fluoride (PVDF) and conductive carbon black are mixed at a weight ratio of 97:2:1, N-methylpyrrolidone (NMP) is added, and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity. The positive electrode functional layer slurry is uniformly coated on the current collector aluminum foil to obtain an aluminum foil coated with the positive electrode functional layer slurry, and the aluminum foil coated with the positive electrode functional layer slurry is dried to obtain an aluminum foil with a positive electrode functional layer on the surface, and the thickness of the positive electrode functional layer is measured to be L, which is 2 μm; then the positive electrode slurry is uniformly coated on the surface of the positive electrode functional layer in the aluminum foil with the positive electrode functional layer to obtain a double-layer coated aluminum foil, and the double-layer coated aluminum foil is dried, and then rolled and cut to obtain the double-layer positive electrode sheet of this embodiment. The thickness of the positive electrode active material layer in the double-layer positive electrode sheet of this embodiment is 50 μm.

[0060] (2) Preparation of double-layer negative electrode sheet: Mix carbon nanotubes and N,N-dimethylbisacrylamide in NMP solvent at a mass ratio of 15:1, and stir under the action of a vacuum mixer until the mixed system becomes a negative electrode functional layer slurry with uniform fluidity. Mix the negative electrode active material graphite, thickener sodium carboxymethyl cellulose (CMC Na), binder styrene butadiene rubber and conductive agent acetylene black at a weight ratio of 97:1:1:1, add deionized water, and obtain the negative electrode slurry under the action of a vacuum mixer. The negative electrode functional layer slurry is uniformly coated on the current collector copper foil to obtain a copper foil coated with the negative electrode functional layer slurry; the copper foil coated with the negative electrode functional layer slurry is dried to obtain a copper foil having a negative electrode functional layer on the surface; the thickness of the negative electrode functional layer is measured to be L, and L is 2 μm; the negative electrode slurry is uniformly coated on the surface of the negative electrode functional layer in the copper foil having the negative electrode functional layer to obtain a double-layer coated copper foil; the double-layer coated copper foil is dried, and then rolled and slit to obtain the double-layer negative electrode sheet of this embodiment; the thickness of the negative electrode active material layer in the double-layer negative electrode sheet of this embodiment is 60 μm.

[0061] (3) Preparation of electrolyte: In a glove box filled with inert gas (H2O <10ppm, O2 <5ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were prepared in a mass ratio of 30:70, and 1 mol / L LiPF6 and 0.5 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of methylene methanedisulfonate (MMDS) and 0.5 wt% of tris(trimethylsilyl)borate (TMSB) in the total amount of the electrolyte were added to obtain a non-aqueous organic electrolyte, and an initiator dibenzoyl peroxide was added to the non-aqueous organic electrolyte, wherein the ratio of the mass of dibenzoyl peroxide to the total mass of N,N-dimethylbisacrylamide in the double-layer positive electrode sheet and the total mass of N,N-dimethylbisacrylamide in the double-layer negative electrode sheet was 0.01.

[0062] (4) Preparation of battery: stack the double-layer positive electrode sheet, separator (9 micron thick PP film), and double-layer negative electrode sheet in order, ensure that the separator is between the double-layer positive electrode sheet and the double-layer negative electrode sheet to play an isolating role, and place the bare battery cell in an aluminum plastic film outer package to obtain a 5Ah battery cell. Inject the electrolyte into the dried battery, encapsulate, stand and form, then perform secondary encapsulation, stand and volume separation to obtain the lithium-ion soft-pack battery of this embodiment.

[0063] Example 2

[0064] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that the thickness L of the positive electrode functional layer on the surface of the aluminum foil is 6 μm.

[0065] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that the thickness L of the negative electrode functional layer on the surface of the copper foil is 6 μm.

[0066] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0067] Example 3

[0068] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that the thickness L of the positive electrode functional layer on the surface of the aluminum foil is 8 μm.

[0069] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that the thickness L of the negative electrode functional layer on the surface of the copper foil is 8 μm.

[0070] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0071] Example 4

[0072] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that N,N-dimethylbisacrylamide and carbon nanotubes are mixed in NMP solvent at a mass ratio of 20:1.

[0073] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that N,N-dimethylbisacrylamide and carbon nanotubes are mixed in NMP solvent at a mass ratio of 20:1.

[0074] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0075] Example 5

[0076] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that N,N-dimethylbisacrylamide and carbon nanotubes are mixed in NMP solvent at a mass ratio of 10:1.

[0077] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that N,N-dimethylbisacrylamide and carbon nanotubes are mixed in NMP solvent at a mass ratio of 10:1.

[0078] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0079] Example 6

[0080] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that bismaleimide is used instead of N,N-dimethylbisacrylamide.

[0081] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that bismaleimide is used instead of N,N-dimethylbisacrylamide.

[0082] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0083] Example 7

[0084] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that conductive carbon is used instead of carbon nanotubes.

[0085] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this embodiment is generally the same as that in Embodiment 1, except that conductive carbon is used instead of carbon nanotubes.

[0086] The preparation of the electrolyte and the battery in this example is the same as in Example 1.

[0087] Example 8

[0088] The preparation method of the electrolyte in this embodiment is generally the same as that in Embodiment 1, except that the ratio of the mass of dibenzoyl peroxide to the total mass of N,N-dimethylbisacrylamide in the double-layer positive electrode sheet and the total mass of N,N-dimethylbisacrylamide in the double-layer negative electrode sheet is 0.05.

[0089] The preparation of the double-layer positive electrode sheet, double-layer negative electrode sheet and battery in this embodiment is the same as that in Embodiment 1.

[0090] Example 9

[0091] Preparation of electrolyte: In a glove box filled with inert gas (H2O <10ppm, O2 <5ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were prepared in a mass ratio of 30:70, and 1 mol / L LiPF6 and 0.5 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of methylene methanedisulfonate (MMDS) and 0.5 wt% of tris(trimethylsilyl)borate (TMSB) accounting for 0.5 wt% of the total electrolyte were added to obtain the electrolyte of this embodiment.

[0092] The preparation of the double-layer positive electrode sheet, double-layer negative electrode sheet and battery in this embodiment is the same as that in Embodiment 1.

[0093] Example 10

[0094] The preparation method of the electrolyte in this embodiment is generally the same as that in Embodiment 1, except that the ratio of the mass of dibenzoyl peroxide to the total mass of N,N-dimethylbisacrylamide in the double-layer positive electrode sheet and the double-layer negative electrode sheet is 0.1.

[0095] The preparation of the double-layer positive electrode sheet, double-layer negative electrode sheet and battery in this embodiment is the same as that in Embodiment 1.

[0096] Comparative Example 1

[0097] (1) Preparation of positive electrode sheet: After the positive electrode active material ternary layered positive electrode, binder polyvinylidene fluoride (PVDF) and conductive carbon black are mixed in a weight ratio of 97:2:1, N-methylpyrrolidone (NMP) is added and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity. The positive electrode slurry is evenly coated on the surface of the aluminum foil to obtain an aluminum foil coated with the positive electrode slurry, and the aluminum foil coated with the positive electrode slurry is dried, and then rolled and cut to obtain the positive electrode sheet of this comparative example. The thickness of the positive electrode active material layer in the positive electrode sheet of the comparative example is 50 μm.

[0098] (2) Preparation of negative electrode sheet: The negative electrode active material graphite, the thickener sodium carboxymethyl cellulose (CMC Na), the binder styrene butadiene rubber and the conductive agent acetylene black were mixed in a weight ratio of 97:1:1:1, and deionized water was added to obtain negative electrode slurry under the action of a vacuum mixer. The negative electrode slurry was evenly coated on the surface of the copper foil to obtain a copper foil coated with the negative electrode slurry. The copper foil coated with the negative electrode slurry was dried, and then rolled and cut to obtain the negative electrode sheet of this comparative example. The thickness of the negative electrode active material layer in the negative electrode sheet of the comparative example was 60 μm.

[0099] (3) Preparation of electrolyte: In a glove box filled with inert gas (H2O <10ppm, O2 <5ppm), ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were prepared in a mass ratio of 30:70, and 1 mol / L LiPF6 and 0.5 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of methylene methanedisulfonate (MMDS) and 0.5 wt% of tris(trimethylsilyl)borate (TMSB) were added to obtain a non-aqueous organic electrolyte.

[0100] (4) Preparation of battery: The positive electrode sheet, separator (9 micron thick PP film), and negative electrode sheet are stacked in order, ensuring that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the bare battery cell is placed in an aluminum plastic film outer package to obtain a 5Ah battery cell. The electrolyte is injected into the dried battery, packaged, allowed to stand, and formed, and then secondary packaging, allowed to stand, and capacity division are performed to obtain the lithium-ion soft-pack battery of this comparative example.

[0101] Comparative Example 2

[0102] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this comparative example is generally the same as that in Example 1, except that the carbon nanotubes are added to the NMP solvent and stirred under the action of a vacuum stirrer until the mixed system becomes a positive electrode functional layer slurry with uniform fluidity.

[0103] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this comparative example is generally the same as that in Example 1, except that the carbon nanotubes are added to the NMP solvent and stirred under the action of a vacuum stirrer until the mixed system becomes a negative electrode functional layer slurry with uniform fluidity.

[0104] The preparation of the electrolyte and the battery in this comparative example is the same as in Example 1.

[0105] Comparative Example 3

[0106] (1) Preparation of double-layer positive electrode sheet: The preparation method of the double-layer positive electrode sheet in this comparative example is generally the same as that in Example 1, except that N,N-dimethylbisacrylamide is added to the NMP solvent and stirred under the action of a vacuum stirrer until the mixed system becomes a positive electrode functional layer slurry with uniform fluidity.

[0107] (2) Preparation of double-layer negative electrode sheet: The preparation method of the double-layer negative electrode sheet in this comparative example is generally the same as that in Example 1, except that N,N-dimethylbisacrylamide is added to the NMP solvent and stirred under the action of a vacuum stirrer until the mixed system becomes a negative electrode functional layer slurry with uniform fluidity.

[0108] The preparation of the electrolyte and the battery in this comparative example is the same as in Example 1.

[0109] Table 1 shows the experimental parameters involved in the preparation process of each embodiment and each comparative example in the present invention.

[0110] Table 1

[0111]

[0112] Performance Testing

[0113] The soft-pack batteries prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were subjected to a room temperature discharge DCR test and a hot box safety test. The test results are shown in Table 2.

[0114] The specific method of the normal temperature discharge DCR test includes: setting the temperature to 25°C, first charging to 4.25 V at a constant current of 1 C, then discharging to 50% SOC at a constant current of 1C, recording the discharge voltage when the discharge capacity reaches 50% SOC as V1, then discharging at a constant current of 2C I for 30s, recording the discharge voltage at this time as V2, and calculating the discharge DCR value, the calculation method is DCR discharge = |V1-V2| / I;

[0115] The specific methods of hot box safety test include: 1. Adjust the battery cell to 100% SOC at room temperature; 2. After fully charged with a clamp of 300kgf, let it stand for more than 2 hours; 3. Heat to 130℃ at 5℃ / min at room temperature and keep warm for 30 minutes; 4. Stop constant temperature and observe for 1 hour; 5. If it has not failed after the end of 4, continue heating to 135℃ and keep the temperature constant for 30 minutes; 6. Heat with a gradient of 5℃ / min and keep the temperature constant for 30 minutes until failure, and record the temperature.

[0116] Table 2

[0117]

[0118] It can be seen from the data in Table 2 that the positive and negative electrodes in Example 1 both have a functional layer of relatively low thickness, which has no effect on electron transmission, has little effect on direct current resistance (DCR), and has a certain improvement in battery safety performance. The positive and negative electrodes in Example 2 both have a functional layer of suitable thickness, which has a certain effect on electron transmission compared with Example 1, the overall DCR increase is controllable, and the degree of safety improvement is also good. The positive and negative electrodes in Example 3 both have a functional layer of relatively high thickness, which has a good degree of safety improvement for the battery, but has a significant effect on electron transmission, and the overall DCR growth increases. In Example 4, the functional layer in the positive and negative electrodes has a high ratio W1 / W2, and the conductive agent content is low, which has a certain effect on electron transmission, and the overall DCR increases; but due to the high content of thermal polymerization monomers, the thermal runaway temperature is increased to a certain extent. In Example 5, the functional layer in the positive and negative electrodes has a low ratio W1 / W2, the conductive agent content is high, and has no effect on electron transmission; but due to the low content of thermal polymerization monomers, the improvement of thermal runaway is reduced. Example 6 replaces the type of thermal polymerization monomer in the functional layer, and the overall difference is not large. In Example 7, the conductive agent in the functional layer is replaced. The specific surface area of ​​conductive carbon is lower than that of carbon nanotubes at the same mass, so its electron transmission is affected to a certain extent, the overall DCR is increased, and the improvement of thermal runaway is also better than that of carbon nanofibers. In Example 8, the electrolyte contains a high content of initiator, and side reactions are likely to occur in the electrolyte, resulting in increased impedance and a certain impact on electrical properties. In Example 9, the electrolyte contains a low content of initiator, and some monomers will spontaneously heat and polymerize, but the thermal polymerization effect is not as good as in Example 1, so the thermal runaway temperature is reduced. In Example 10, the electrolyte contains too high a content of initiator, and more side reactions are likely to occur in the electrolyte, and there is no improvement in safety performance. The functional layer in Comparative Example 2 has no thermally polymerized monomers, and has no effect on thermal runaway compared to Comparative Example 1. The functional layer in Comparative Example 3 has no carbon nanotubes, the polymerized monomers do not conduct electrons, and the battery cell cannot operate normally.

[0119] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A battery, characterized in that: The battery comprises an electrode sheet; The electrode sheet comprises a current collector, a functional layer and an active material layer, wherein the functional layer is arranged on at least one surface of the current collector along the thickness direction, and the active material layer is arranged on the surface of the functional layer away from the current collector; the functional layer comprises a conductive agent and a thermally polymerizable monomer; In the functional layer, the conductive agent and the thermal polymerization monomer satisfy the relationship: 10≤W1 / W2≤20, wherein W1 represents the mass proportion of the thermal polymerization monomer in the functional layer, and W2 represents the mass proportion of the conductive agent in the functional layer; The thermally polymerizable monomer is selected from at least one of acrylamide, N,N-dimethylbisacrylamide, bismaleamide and nadic anhydride; The electrode sheet is a positive electrode sheet and / or a negative electrode sheet.

2. The battery according to claim 1, characterized in that The thickness of the functional layer is 2-8 μm.

3. The battery according to claim 1, characterized in that The conductive agent includes a one-dimensional conductive agent; the radial length of the one-dimensional conductive agent is 0.5-8 μm.

4. The battery according to claim 3, characterized in that The one-dimensional conductive agent is selected from at least one of carbon fibers, carbon nanotubes and copper nanotubes.

5. The battery according to claim 1, characterized in that The battery further comprises a non-aqueous organic electrolyte containing an initiator.

6. The battery according to claim 5, characterized in that In the battery, the initiator and the thermal polymerization monomer satisfy the following relationship: W3 / W4≤0.05, wherein W3 represents the mass of the initiator in the non-aqueous organic electrolyte, and W4 represents the mass of the thermal polymerization monomer in the battery.

7. The battery according to claim 6, characterized in that The initiator is selected from dibenzoyl peroxide and / or azobisisobutyronitrile.

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